exam 3 part 2

Question 1

1o / primary sex ratio

Answer 1

sex ratio at fertilization – theoretical 1:1 more like 115:100 males/females in humans

Question 2

2o / secondary sex ratio

Answer 2

sex ratio at birth or hatching
-skewed towards males in mammals
Ratio - 105:100 males to females in humans

Question 3

how is secondary sex ration skewed toward males in mammals (3)

Answer 3

-male numbers decrease rapidly and ratio favors females
-younger females tend to produce more male offspring
-first offspring at any age tends to be male

Question 4

why is secondary sex ration skewed toward males in mammals

Answer 4

-Problems with heterogametic sex
-males (XY) are more likely to exhibit issues from recessive mutations on the X chromosome than females (XX)

Question 5

3o / tertiary sex ratio

Answer 5

-sex ratio at sexual maturity
-decreases in males as we age because Greater mortality to violence; increased risk of many diseases

*fourth decade (30’s), 100:100
*seventh decade (60’s), 87.5:100
*Ninth decade (80’s), 41:100

Question 6

4o sex ratio

Answer 6

sex ratio of the adult population

Question 7

Fisher’s Principle

Answer 7

a theory in evolutionary biology that explains why the sex ratio in sexually reproducing species is usually close to 1:1

Question 8

how Fisher’s Principle works (4)

Answer 8

-If there’s less males than females, males have less competition
-Because reproduction advantage is high more males are born
-With more males competition is higher, decreasing reproductive advantage
-This leads to less males being born, repeating the cycle

Question 9

Evolutionarily Stable Strategy (ESS)

Answer 9

-1:1 sex ratio is common in most species →evolutionarily stable strategy
-once at stable state natural selection maintains state

Question 10

Extinction causes / increase probability of extinction
(3)

Answer 10

When death rate > birth rate

R= net reproduction rate
When R<1

r = instantaneous rate of population growth
When r is negative

Question 11

Deterministic Extinction

Answer 11

-inescapable force causes extinction

-Asteroid at K-T boundary
-Habitat destruction

Question 12

Stochastic Extinction

Answer 12

normal random fluctuations affect small populations more
two types

Question 13

Demographic stochasticity

Answer 13

chance change in birth and/or death rate

Question 14

Environmental stochasticity

Answer 14

chance decrease in population (may lead to demographic stochasticity)

Question 15

Vulnerability to extinction varies by species

Answer 15

Common, abundant species may be less vulnerable, NOT impervious

Question 16

Extinction vortex concept

Answer 16

a self-reinforcing process in which small populations are increasingly likely to decline toward extinction

Question 17

Niche

Answer 17

functional role of species in ecosystem

Question 18

Causes of modern extinction

Answer 18

Habitat destruction
–Dusky Seaside Sparrow

overhunting/overharvesting
– Steller’s Sea Cow, Tasmanian Wolf

Introduction of exotics:
–competitors, – Chestnut Blight
–pests,pathogens, – Brown Tree Snake

Predator and pest control
–the dodo bird extinction leading to calvaria tree decline

Question 19

Effective population size, Ne

Answer 19

Ne = (4 x Nm x Nf) / (Nm + Nf)

Question 20

Ideal population concept (4)

Answer 20

Constant population size
Equal sex ratio
Equal probability of mating
Constant dispersal rate

Question 21

Minimum viable populations (MVP)

Answer 21

the smallest population size of a species that is considered necessary to ensure its long-term survival

Question 22

50/500 Rule (2)

Answer 22

-a minimum population size of 50 is needed to prevent inbreeding depression
-500 is needed to reduce genetic drift

California condors

Question 23

Community

Answer 23

all individuals of all species living within 1 habitat at given time

Question 24

Interspecific

Answer 24

among members of different species

Question 25

Intraspecific

Answer 25

among members of a single species

Question 26

neutral interactions

Answer 26

(0,0) → snail, ladybug

Question 27

commensalism interactions

Answer 27

(0,+) → Spanish moss on live oak

Question 28

amensalism interactions

Answer 28

(0,-) → Penicillium and S. aureus

Question 29

consumption interaction

Answer 29

(+,-) → deer browsing on shrub leaves; wolf eating deer

Question 30

competition interaction

Answer 30

(-,-) → squirrels vs. chipmunks

Question 31

mutualism

Answer 31

(+,+) →humans and gut flora

Question 32

parasitism

Answer 32

(+,-) → humans and tapeworms

Question 33

The competitive exclusion principle (CEP)

Answer 33

two species cannot coexist indefinitely if they compete for the same resources and have identical niches